Radio access networks (RANs) provide for radio communication links to be arranged within the network between a plurality of user terminals. Such user terminals may be mobile and may be known as ‘mobile stations’ or ‘subscriber devices.’ At least one other terminal, e.g. used in conjunction with subscriber devices, may be a fixed terminal, e.g. a control terminal, base station, eNodeB, repeater, and/or access point. Such a RAN typically includes a system infrastructure which generally includes a network of various fixed terminals, which are in direct radio communication with the subscriber devices. Each of the fixed terminals operating in the RAN may have one or more transceivers which may, for example, serve subscriber devices in a given region or area, known as a ‘cell’ or ‘site’, by radio frequency (RF) communication. The subscriber devices that are in direct communication with a particular fixed terminal are said to be served by the fixed terminal. In one example, all radio communications to and from each subscriber device within the RAN are made via respective serving fixed terminals. Sites of neighboring fixed terminals may be offset from one another or may be non-overlapping or partially or fully overlapping.
RANs may operate according to an industry standard protocol such as, for example, an open media alliance (OMA) push to talk (PTT) over cellular (OMA-PoC) standard, a voice over IP (VoIP) standard, or a PTT over IP (PoIP) standard. Typically, protocols such as PoC, VoIP, and PoIP are implemented over broadband RANs including third generation and fourth generation networks such as third generation partnership project (3GPP) Long Term Evolution (LTE) networks. Communications in accordance with any one or more of these standards, or other standards, may take place over physical channels in accordance with one or more of a TDMA (time division multiple access), FDMA (frequency divisional multiple access), OFDMA (orthogonal frequency division multiplexing access), or CDMA (code division multiple access) protocols. Subscriber devices in RANs such as those set forth above send and receive speech and data, herein referred to collectively as ‘traffic information’, in accordance with the designated protocol.
OMA-PoC, in particular, is a recent technology that enables familiar PTT and “instant on” features of conventional half duplex radios, but uses mobile subscriber devices operating over modern cellular telecommunications networks. Using PoC, wireless subscriber devices such as mobile telephones and notebook computers can function as PTT half-duplex radio devices for transmitting and receiving voice and/or data. Other types of PTT models and multimedia call models (MMCMs) are also available.
Floor control in an OMA-PoC session is generally maintained by a PTT server that controls communications between two or more wireless subscriber devices. When a user of one of the subscriber devices keys a PTT button, a request for permission to speak in the OMA-PoC session is transmitted from the user's device to the PTT server using, for example, a real-time transport protocol (RTP) message. If no other users are currently speaking in the PoC session, an acceptance message is transmitted back to the user's device and the user can then speak into a microphone of the device. Using standard compression/decompression (codec) techniques, the user's voice is digitized and transmitted using discrete voice data packets, such as according to RTP and internet protocols (IP), to the PTT server. The PTT server then transmits the voice data packets to other users of the PoC session, using for example a point to multipoint communication technique.
Group call interconnections may be made between wireless and/or wireline participants via the Internet or other wide area network, for example. Typically, members of groups for group calls are statically defined. That is, a user, or administrator working on behalf of the user, indicates to the switching and/or or radio network (perhaps at the PTT server) a list of participants of a talk group at the time of the call or in advance of the call. The group members could be provisioned in the network by the user or an agent, and then provided some form of group identity, for example, to make the call. Then, at a future time, an originating user may perform some signaling to indicate that he wishes to establish a communication session (e.g., group call) with each of the pre-designated participants in the defined talk group.
As many of these subscriber devices are small and portable, they rely upon a limited direct current (DC) battery supply to operate throughout the day. Given the limited amount of power that can be stored in a small form factor battery used by such subscriber devices, conserving power to extend battery life has emerged as an important design priority. As such, subscriber devices are conventionally configured to enter a low-power or power-save state during idle times, during which time the subscriber device may shut down one or more components, including wireless interfaces, thereby conserving battery power for when it is most needed. While utilization of this low-power state may provide power conservation, problems may arise in setting up a group call to a large group of subscriber devices over a wide-area network such as the Internet when many of those members may be in a lower-power state and may be difficult to reach.
For example, call setup for a subscriber device when a new group call is received, where the subscriber device is already active and in a “connected” state with its serving RAN (e.g., already has a data channel assigned), can normally be completed in less than 1 s. If, however, the subscriber device is in a low-power state and only periodically waking up and briefly checking a control channel for paging indications (e.g., new call notifications) before returning to its low-power state, call setup for group calls involving such a subscriber device can take on the order of 5-15 s. This delay becomes more meaningful and problematic when applied in situations such as first responder dispatches, where small delays in call setup time can be quite detrimental to the health and/or welfare of the people or property the first responders are protecting.
Accordingly, there is a need for an improved method and apparatus for reducing paging delay in a RAN that allows a subscriber device to anticipate the arrival or generation of new private or group calls, and prevent itself from entering a low-power state so as to improve call setup times under such circumstances.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.
The apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.